Method for purification of amyl alcohols



April 14, 1953 T. Q. ELIO-r METHOD FOR PURIFICATION OF AMYL ALCOHOLS Filed Dec. 30, 1950 Patented Apr. 14, Y1953 UNITED STATES PATENT OFFICE METHOD FOR PURIFICATION OF AMYL ALC OHO

Theodore Q. Eliot, Tulsa, Okla., assignor to Stanolind Oil and Gas Company, Tulsa, Okla., a. corporation of Delaware Application December 30, 1950, Serial No. 203,715

" trope with or which boil close to the boiling point of such alcohols. More particularly, it pertains to a method for separating various of the amyl alcohols from ketones which either azeotrope therewith such as, for example, cyclopentanone and methylcyclopentanone, or which boil so close to the boiling point of said Various amyl alcohols that separation by means of straight fractional distillation is impossible.

Mixtures containing n-pentanol, 2-methyl-1- butanol and S-methyl-l-butanol, or at least one of these alcohols together with at least one of the aforesaid ketones, cannot be satisfactorily separated by means of ordinary fractional distillation methods owing to the fact that 2-methyll-butanol and S-methyl-l-butanol, which boil at 128.9 C. and 132 C. respectively, form azeotropes with cyclopentanone (B. P. l30.7 C.) boiling at approximately 127.0 C. and 129.5 C. respectively, while 2 methylcyclopentanone, which boils at 13B-139 C., cannot be separated from n-pentanol boiling at 138.0 C. Although the problem of separating various of the abovementioned amyl` alcohols from cyclopentanone or 2-methy1cyclopentanone occurs in numerous purification procedures, one of the principal instances where an efficient method for the separation of these compounds is most urgently needed is in their recovery, along with other chemicals, from both the water and ,oil fractions producedk by the reduction of carbon monoxide with hydrogen i-n the presence of a fluidized alkali-promoted iron catalyst under known synthesis conditions. The magnitude of this problem may be more fully appreciated when it is realized that in hydrocarbon synthesis plants designed for commercial operation and having a capacity of about 6,000 bbls. per day of liquid hydrocarbons, there are produced in the water stream alone 'approxivmately 4200 lbs. of amyl alcohols per dayand about 1000 lbs. per day of cyclopentanone and Z-methylcyclopentanone. Both classes of these compounds are found in the oil stream in even -greater amounts than they normally occur in boiling residue, 40 to 50 per cent of which consists of various carbonyl fractions. Mixtures `of this type can generally be separated initially into three fractions, i. e., (1) a portion consisting chiefly of 2-methyl-1-butanol, S-methyl-l-butanol, and cyclopentanone, (2) a fraction of npentanol and 2-methylcyclopentanone, and (3) a fraction consisting of compounds boiling above about 137-140 C. Further distillation of the first two fractions is ineective to separate the components thereof owing to the fact that azeotropes are formed in each instance.

Attempts have previously been made to separate the above-mentioned amyl alcohols from one another and from the aforesaid ketones by distilling the crude mixture containing these alcohols and ketones up to a temperature of about 87 C. Thereafter, a second fraction boiling from about 87 C. to about 138 C. was collected, after which the resulting distillate was azeotropically distilled with water until the overhead being obtained was substantially free of ketones. Distillation of the mixture vunder such conditions yielded a bottoms of n-pentanol and an overhead fraction containing 2-methyl-1- butanol and S-methyl-l-butanol, cyclopentanone, 2-methylcyclopentanone, and a small amount of n-pentanol. This overhead fraction Was distilled until all of the water had been removed, after which the resulting dry mixture of alcohols and ketones was subjected to distillation under a pressure of about 40 mm. By this operation, however, a sizeable fraction boiling from about 54 C. to about 62 C. (40 mm.)4 was obtained which contained the bulk of the 2-methy1-1- butanol and the B-methyl-l-butanol together with a large portion of both ketones which passed overhead along with the alcohols. In order to effect a separation between these alcohols and ketones, the distillate collected at 54 C. to 62 C. (40 mm.) was subjected to distillation at atmospheric pressure whereby there were obtained two overhead fractions; one boiling at C. and the other boiling at about 138 C. to C. The bottoms fraction was relatively small and consisted essentially of high-boiling ketone polymers. The aforesaid fraction boiling at about 130 C. contained approximately 90 per cent alcohols (2-methyl-1-butanol and f3- methyl-l-butanol) but Was still contaminated with about 10 per cent ketones, whereas approximately 75 per cent of the Z-methylcyclopentanone was obtained in a relatively pure conditionin the fraction boiling at 138 C.,to 140 C. The above procedure suffers several serious .disadvantages. Because of the large number of repeated distillations, considerable mechanical losses of materials occur, and the heat-sensitive ketones are polymerized. In addition, a large amount of high-vacuum distillation equipment is necessary, since all the iso C5 alcohols and both cyclic ketones must be distilled at about 4 0 mm. Finally, the separation does not completely resolve the mixture, since a final fraction is obtained at 130 C. (760 mm.) which contains appreciable amounts of both iso-alcohols and Z-methylcyclopentanone.

Accordingly, it is an object of my invention to provide a simplified and eillcient method for separating the aforesaid isomeric amyl alcohols from ketones such as, for example, cyclopentanone and Z-methyl-cyclopentanone. It is still a further object of my invention to provide a method whereby said alcohols and ketones can be readily separated from one another and recovered in substantially pure form.

I have now discovered that the foregoing disadvantages in the previous methods for effecting the aforesaid separation can be avoided and that each of the desired components in the mixtures of the type mentioned above can be recovered in a state of high purity. In accordance with the process of my invention, separation of such mixtures is effected by rst removing the light impurities contained therein by fractionally distilling said mixture up to a temperature of from about 118 C. to about 126 C., preferably about 121 C. Thereafter, the bottoms from this distillation operation is subjected to further fractionation up to a temperature of about 137 C. to 140 C. to bring overhead a mixture of the various amyl alcohols, cyclopentanone and 2-methylcyclopentanone, while a residue consisting of high-boiling impurities is withdrawn from the base of the still. The resulting distillate is next subjected to further fractional distillation in the presence of Water. This operation is continued until the ketone content of the organic product layer being collected is not more than about 2 weight per cent, as determined by the standard hydroxylamine test or similar techniques. The bottoms fraction thus obtained consists of essentially pure n-pentanol, while the distillate consists of 2-methylcyclopentanone, cyclopentanone, 2 -mcthyl-1-butanol, 3-methyl-1-butanol, and Water together with a small amount of n-pentanol. The latter mixture is then dried in accordance with any suitable procedure. For example, I generally prefer to accomplish this object by distilling the Water oi in the form of a constant boiling mixture With the various alcohols and ketones. These alcohols and ketones, which are substantially insoluble in Water, form an upper layer in the resulting distillate that is drawn off and recycled to the distillation column. Ultimately, an anhydrous mixture is obtained consisting of 2-methylcyclopentanone, cyclopentanone, 2-methyl-1-butanol and B-methyl-l-butanol, together with a small quantity of n-pentanol which Was carried over in the previous distillation step to insure the procurement of a bottoms of substantially pure n-pentanol. After this mixture has been thoroughly dried, it is next fractionally distilled to obtain overhead an azeotrops-containing mixture of cyclopentanone, 2- methyl-l-butanol and S-methyl-l-butanol boiling in the range of 127 C. to 132-134o C. The bottoms fraction thus obtained consists largely of 2-methylcyclopentanone, the balance being npentanol. Thereafter, both the overhead and bottoms fractions are separately distilled under reduced pressure to effect a separation of the remaining components of each mixture. Thus, in the case of the distillate or overhead fraction, cyclopentanone is separated from 2-methyl-1- butanol and B-methyl-l-butanol by fractionation of the mixture at a pressure of from about 40 to 200 mm., While the mixture consisting of 2-methylcyclopentanone and n-pentanol is subjected to distillation at pressures of from about 40 to 150 mm. In both instances, distillation is generally preferably effected at pressures in the neighborhood of mm.

To summarize, a preferred embodiment of my invention comprises the following steps:

(1) Distillation of the crude mixture of alcohols and ketones up to about 121 C. to remove 4light impurities.

(2) Further fractionation of the residue from step (1) and collecting distillate boiling up to about 138 C.

(3) subjecting the distillate vobtained in step (2) to distillation in the presence of Water and continuing distillation until the ketone content of the organic product layer being collected is less than about 2 weight per cent, giving a bottoms fraction consisting of n-pentanol.

(4) The overhead fraction from step (3) which consists of cyclopentanone, 2j-methylcyclopentanone, 2-methyl-l-butanol, S-methyl-l-butanol, some n-pentanol and Water, is dried.

(5) The dry mixture obtained in step (4) is fractionally distilled up to about 132-134" C.

(6) rlhe distillate obtained in step (5) is fractionally distilled under pressure of about 100 mm. to yield an overhead of substantially pure cyclopentanone and a bottoms of the two branchedchain amyl alcohols.

(7) The bottoms produced in step (5) is like- Wise distilled at about 1GO mm. to yield pure 2- methylcyclopentanone overhead leaving a bottoms fraction of n-pentanol.

For a better understanding of the process of my invention an example is given below illustrating the principles thereof as applied to a higher alcohols fraction obtained from a plant processing Water-soluble chemicals produced in hydrocarbon synthesis.

Example A crude aqueous mixture vof higher alcohols having the following composition was selected to be refined in accordance With the invention described above:

Weight per cent Component: (dry basis) n-Butanol 5 Z-methyl-l-butanol 8 3-methyl-1-butanol 6 Cyclopentanone 11 2methylcyclopentanone 7 n-Pentanol 40 Fraction boiling above 140 C (760 The above mixture Was next distilled and fractions selected at 126 C. and at 137.5 C. The fraction boiling up to 126 C. contained principally n-butanol and water and amounted to 6.5 weight per cent of the mix-ture distilled. The fraction boiling between 126 C. and 137.5n C. consisted essentially of the C5 alcohols, both normal and branched-chain, cyclopentanone and 2- methylcyclopentanone. This fraction 'was 'com-J lected is less than 2 weight per cent. The distillate from this operation had the following composition (dry basis):

35.5 weight per cent branched-chain amyl alcohols, 28.2 weight cyclopentanone, v16.4 weight,

per cent n-pentanol and 19.9 weight percent 2- methylcyclopentanone, while the bottoms (dry basis) consisted of 99.5 weight per cent n-pentanolV and v0.5 weight per cent 2methylcyclopen tanone.

The above overhead or distillate portion was next distilled to remove the water contained therein in the form of constant boiling mixtures with the C5 alcohols and the C5 and C6 ketones,A

after which cuts were taken, during distillation, of the resulting dry mixture at 124 C. to 134 C. and at 134 C. to 138 C. The rst fraction consisted of 52 Weight per cent branched-chain amyl alcohols, 41.5 weight per centcyclopentanone and 6.5 weight per cent 2-methylcyclopentanone, while the 134 C. to 138 C. cut contained 49 weight per cent Z-methylcyclopentanone and 51 weight per cent n-pentanol. These fractions were next separately distilled at 40 mm. The fraction previously collected up to 134 C. yielded an overhead boiling at 49 C. and consisted of cyclopentanone which was 96.5 per cent pure. From 49 C. to 55 C., a fraction was obtained which analyzed 66 per cent cyclopentanone, and

at 61 C. to 63 C. an overhead was collectedv yield (as bottoms) 69 per cent of the n-pentanol in the charge as pure ketone-free material.

About 64 per cent of the 2-methylcyclopentanone was recovered inthe distillate, its purity being 89 per cent.

The process of my invention is further illustrated by the accompanying flow diagramY in which a crude mixture of amyl alcohols derived from the separation of n-butanol and lighter alcohols present in the hydrocarbonv synthesis product Water stream is introduced at an intermediate point in column 2 through line 4. Within column 2, which is operated so as to remove light impurities boiling up to about 121 C., light impurities are withdrawn through line 6 and condenser 8, while a portion of this stream is returned to the column throughy line I0 as reflux. After low-boiling impurities have been removed in this manner, the residue thus obtained is withdrawn from column 2 through line I2 and passes into column vI4 where afraction boiling up to about 138 C. is taken overhead through line I6 and condenser I8. Part of the stream thus removed from column I4 is returned thereto via line 2Ilwhile the remainder passes into column 22. Withdrawal of high-boiling impurities from column I4 is effected through line I5. The stream introduced into column 22 consists essentially of Csialc'ohols, both normal and branchedchain, cyclopentanone and 2-methylcyclopen- 6., tanone. Prior to introduction of the aforesaid stream into column 22, it ismixed with water added through line 24. Water is added at this point to permit all of the components of the stream withdrawn from column I4, with the exception of n-pentanol, to pass overhead Athrough line 26 and condenser 28 in the form of their water azeotropes. This distillation is operated under conditions such that both ketones, the branched-chain alcohols and a small amount of n-pentanol are removed in the distillate. The bottoms fraction thus obtained in column 22 is substantially free from ketones or, at most, contains not more than about 0.5 weight per cent. During distillation, part of the stream withdrawn through line 26 is returned as reflux to column 22 via line 29. Wet n-pentanol, free from ketones and branched-chain alcohols, is withdrawn from the bottom of column 22 through line 30. The stream coming from condenser 28 is sent to cooler 3I, after which it flows into separator 33 where it settles out into two layers, the lower Water layer being recycled to column 22 through line 35. The organic product layer is withdrawn through line`3I and introduced into drying column 32 where removal of the water therefrom is effected by withdrawing aqueous azetropes of the alcohols and ketones contained therein through line 34 and condenser 36, after which these azeotropes are introduced into separator 38 where they are allowed to stratify into two layers. The upper layer, or organic phase, is withdrawn through line 40 and is returned to column 32 while the lower water layer is removed from separator 38 via line 42 and recycled to the system through line 24. Excessive build-up of water-soluble` impurities in this water layer may be prevented by periodically withdrawing a stream through line 43. A portion of the stream withdrawn through line 34 is returned to column 32 `as reflux through line 44. The dry lbottoms in column 32 which consists of 2-methyl-1-butanol, B-methyl-lbutanol, n-pentanol, cyclopentanone and 2- methylcyclopentanone iswithdrawn through line 46A and passed into column 48'which is operated at132 C. to 134 C. (vapor temperature). Within this column, a vaporous mixture of 2-methyll-butanol, ,Ii-methyl-l-butanol and cyclopentanone is broughtY overhead through line 49 and condenser 50 and introduced to low pressure column 52. Part of the Y stream withdrawn through line 49 is returned to column 48 as reux via line 53. In low-pressure column 52, which is operated at about 100 mm., cyclopentanone is brought overhead through line 54 and condenser 56 at a temperature of about 71 C., a portion .of this stream being returned to the column as reflux through line 58. The bottoms fraction obtained by this operationis withdrawn through linell and consists of substantially pure Z-methyl-l-butanol and 3- methYl-l-butanol. The bottoms fraction in column 48 is removed therefrom through line 62 and introduced into low-pressure column 64 where separation betweenl -v2-methylcyclopentanone and n-pentanol is effected. kThis low- Dressure column is likewise operated at about 100mm., 2-methylcyclopentanone being removed overhead through line 66 and condenser B8 at av temperature of about CI Reiiux to the colume of a portion of the stream withdrawn via line 66 is maintained by returning a small stream through line 10. Ketone-free n-pentanol is withdrawn from the column through line '12.

Apheric pressures, Also, the expression close-boiling ketones as used herein is intended to include both ketones asesoragram illustrateV advantageous embodiments' of my invention, it ls to be understood that the scope thereof is not. limited thereto. On the contrary, my invention is tov be construed broadly with respect to the present description and claims; and, in general, it` is to be understood that any modications of equivalents Which would normally occur to those skilled in the art are to be considered as lying within the scope of my invention.

Throughout the present description and claims, vall boiling points referred to are the boiling points of the compounds in question at atmosunless otherwise indicated.

which azeotrope with the alcohol or alcohols yconcerned or which actuallyk boil so close thereto that separation. of the alcohol or alcohols therefrom cannot be eiected by ordinary distillation techniques. In azeotroping operations involving distillation in the presence of water, it is assumed that the resulting bottoms may be wet, depending on whether or not the operation is carried out batchWise or continuously and depending upon the amount of water added during distillation.

What I claim is:

1.. In a process for the recovery of Z-methyll-butanol and B-methyl-l-butanol from mixtures containing n-pentanol and ketones wherein some of said ketonesl azeotrope with n-pentanol and some azeotrope with. 2`methyl1butanol and S-methyl-l-butanol, said mixture having a boiling range from about 121 C. to about 139 C.; the steps which comprise subjecting said mixture to distillation in the presence` of at least suicient water to forni` azeotropes with all of' said 2-methyl-1-butanolr S-methyl-l-butanol and said ketones; continuing this distillation until the ketone content of the organic product layer being collected is not more than about 2 Weight per cent, drying the overhead fraction obtained in said last-mentioned distillation step, thereafter subjecting the resulting dry mixture to fractional distillation, collecting a distillate up toy about. 132-134? C'., and subjecting this distillate toA further fractionation at a pressure of from about 40 to about 209 mm. to obtain everhead substantially pure cyclopentanone leaving a bottoms fraction consisting of substantially pure 2-methyl-1-butanol and S-methyl-l-butanol.

2. In a process for the recovery of n-pentanol, Z-methyl-l-butanol and S-methyl -lbutanol from dry' mixtures thereof' containing ketones wherein some of said ketones azeotrope withy n-pentanol and someV azeotrope with Z-methyl- 1butanol and 3methyll-butanol, the steps which comprise` subjecting said mixture tol distillation and collecting a fraction boiling' fromabout 121 C. upl to about 132-134"v C., thereafter further fractionating said distillate at' a pressure of from about 40 to about 200 m-m. to obtain a bottomsE fraction of substantiallyv pure 2-methyl-l-butanol and B-methyl -1- butanol, subjecting that portion of the aforesaid mixture boiling above 134 C. to further fractional dis- .tillation at a pressure of' from about 40j to' about '0 mm., continuing this distillation until' the ketone contenti of the; organic product layer. being collected is lessv than about, 2 weightper cent,l .and recovering` a. bottoms of; substantially pure `n-pentanol.

3. In a. process for the recovery of n-pentanol` from mixtures` containing. Z-methyl-l-butanol,

B-methyl-l-butanol and ketones wherein some of said ketones azeotrope with n-pentanol and some. azeotrope with Z-methyl-l-butanol and a-methyl-l-butanol, the steps which comprise subjecting said mixture to distillation, collecting a fraction boiling from about 121 C. to about 139 C., consisting essentiallyV of n-pentanol, 2-methyl-1-butanol, B-methyl-l-butanol and said ketones, thereafter subjecting the fraction thus collected to distillation in the presence of at least sufficient water to form azeotropes with all of' said 2methyl-1butano1, 3methyl1butanol and said ketones, and continuing the distillation until the ketone content of the organic product layer bei-ng collected is not more than about 2 Weight per cent to thereby obtain a bottoms fraction consisting essentially of n-pentanol free from said ketones, Z-methyl-l-butanol and S-methyl- 1butanol.

4. In a process for the recovery of n-pentanol, 2`methyl1butanol and B-methyl -lbutanol from mixtures containingA ketones wherein some of said ketones azeotrope with n-pentanol and some azeotrope with Z-methyl-l-butanol and 3- methyl-l-butanol, the steps which comprise subjecting said mixture to distillation, isolating a fraction boiling from about 121 C. to about 139 C., subjecting the resulting fraction to further distillation in the presence of at least suicient water to azeotrope With said Z-methyl-l-butanol, B-methyl-l-butanol and said ketones, continuing said distillation until the ketone content of the organic product layer being collected is not more than about 2 Weight per cent to thereby obtain a bottoms fraction consisting ofl substantially pure n-pentanol, drying the overhead fraction obtained in said last-mentioned distillation step, thereafter subjecting the resulting dry mixture tofractional distillation and collecting a distillate up to about 132-134" C., subjecting this distillate to further fractionation at a pressure of about 40 to about 200 mm. to obtain a bottoms fraction consisting of substantially pure Z-methyl-lbutanol and B-methyl-l-butanol.

5. The process of claim 4 in which the mixture being distilled contains from about 12 to 15 per cen-t cyclopentanone, 6' to 10 per cent 2'- methylcyclopentanone, 40 to 50 per centl n-pentanol, 7 to 10 cent 2methyl-1butanol, and 8` to 11 per cent B-methyl-l-butanol.

6. In a process forV the recovery of Z-methyl-lbutanol and S-methyl-l-butanol from mixtures containing n-pentanol and ketones wherein some of said ketones azeotrope with n-pentanol and some azeotrope With 2methyl1butanol and 3- methyl-l-butanol, said mixture having a boiling range of from about 121 C". to about 139 C., the steps which comprise subjecting said mixture to distillation in the presence of at least sufficient water to form azeotropes with all of said 2'- methyl-l-butanol, 3methyl1butanol and' said ketones, continuing this distillation until the ketoneV content of the` organic product layer being collected is not more than about 2 Weight perI cent', drying thel overhead fraction obtained in said last-mentioned distillation step, thereafter subjecting the resulting'dry mixture to fractional distillation, collecting a distillate up to about 132-134ADV C., and subjecting this distillate to further fractionation at a pressure of from about 40. to about 200 mm. to. obtain overhead substantially purey cyclopentanone, leaving ay bottoms fraction consisting of substantially pure 2- methyl-l-butanol and S-methyl-l-butanol.`

7.. In. a.- continuous processv for. the recovery of' n-pentanol from a mixture boiling from about 121 C. to about 139 C. and containing Z-methyll-butanol. 3-methyl -1- butanol and ketones wherein some of said ketones azeotrope with npentanol and some azeotrope with 2-methyl-1- butanol and S-methyl-l-butanol, the steps which comprise subjecting said mixture to distillation in the presence of at least suicient Water to form azeotropes with all of said 2-methyl-1-butanol, B-methyl-l-butanol and said ketones, Withdrawing a bottoms fraction of n-pentanol substantially free from 2-methyl-1-butanol and 3- methyl-l-butanol and containing not more than about 0.5 Weight per cent ketones, and repeating the above cycle.

10 8. The process of claim 1 in which the pressure employed in the low pressure distillation step is approximately 100 mm.

THEODORE Q. ELIOT.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,324,255 Britton et al. July 13, 1943 2,551,584 Carlson et al May 8, 1951 2,551,593 Gilliland et al. May 8, 1951 2,551,624 Morrell et al May 8, 1951 2,552,911 Steitz May 15, 1951 2,564,200 Grehel Aug. 14, 1951 

3. IN A PROCESS FOR THE RECOVERY OF N-PENTANOL FROM MIXTURES CONTAINING 2-METHYL-1-BUTANOL, 3-METHYL-1-BUTANOL AND KETONES WHEREIN SOME OF SAID KETONES AZEOTROPE WITH N-PENTANOL AND SOME AZEOTROPEWITH 2-METHYL-1-BUTANOL AND 3-METHYL-1-BUTANOL, THE STEPS WHICH COMPRISE SUBJECTING SAID MIXTURE TO DISTILLATION, COLLECTING A FRACTION BOILING FROM ABOUT 121*C. TO ABOUT 139*C., CONSISTING ESSENTIALLY OF N-PENTANOL, 2-METHYL-1-BUTANOL, 3-METHYL-1-BUTANOL AND SAID KETONES, THEREAFTER SUBJECTING THE FRACTION THUS COLLECTED TO DISTILLATION IN THE PRESENCE OF AT LEAST SUFFICIENT WATER TO FORM AZEOTROPES WITH ALL OF SAID 2-METHYL-1-BUTANOL, 3-METHYL-1-BUTANOL AND SAID KETONES, SAID CONTINUING THE DISTILLATION UNTIL THE KETONE CONTENT OF THE ORGANIC PRODUCT LAYER BEING COLLECTED IS NOT MORE THAN ABOUT 2 WEIGHT PER CENT TO THEREBY OBTAIN A BOTTOMS FRACTION CONSISTING ESSENTIALLY OF N-PENTANOL FREE FROM SAID KETONES, 2-METHYL-1-BUTANOL AND 3-METHYL1-BUTANOL. 